Here are several alternate system definitions some of which have known solutions which can be used to debug modifications to the code.
Parabolic, circular and elliptic orbits are each computed here. In each case of two orbiting masses, one is so light that it should not affect the other. For the circle the computed results are compared with the circle as defined by sin and cos. The parabola case ejects one particle that escapes to infinity with 0 total energy. That 1-x-yy/4 stays small shows that the orbit is indeed a parabola. Some notes on the ellipse.
The 345 configuration is inaugurated here together with instructions for the plot.
Falling from infinity with zero total energy is performed here with tweaks of the impact parameter.
These are the periodic solutions proposed here. One step of improvement has been taken.